It is desirable for inflatable restraint systems having intergrally formed air bag doors to include some means of insuring that the air bag doors break and/or tear open in a generally predictable way. This is true for driver-side inflatable restraint systems (DSIRs), passenger-side inflatable restraint systems (PSIRs) and inflatable restraint systems in vehicle door panels, quarter panels; other sidewall structures, seats, headliners, pillars, etc. The air bag doors in such systems open to provide a path for an air bag to deploy through. It is also desirable for such systems to include means for insuring that portions of the door do not separate from the system when an air bag deploys and forces the door open.
To develop tearing and/or breaking, air bag doors that are integrally formed with automotive trim or instrument panels will sometimes include regions of weakened materials, reduced thickness or scoring, all of which are commonly referred to as "tear seams." Tear seams are weak areas designed to tear and/or break when an air bag inflates and forces the door to open. Some of these systems also employ tethers and/or hinges that retain the air bag door to the instrument or trim panel after the door has torn and/or broken open. For example, U.S. Pat. No. 5,569,959, issued to Cooper et al., discloses an inflatable restraint assembly comprising an air bag door retainer portion integrally formed in an automotive instrument panel retainer and defined by a door seam. A tear guide is included in a skin cover disposed over a foam layer that extends across the door opening. A metal hinge panel is embedded within the instrument panel retainer and spans a portion of the door seam. Cooper et al. also disclose a method for making such an inflatable restraint assembly. The method includes pre-molding the hinge panel into the hard instrument panel retainer portion such that the hinge panel spans the door seam.
With many current systems, the tear seams and/or hinges are formed in a hard instrument panel retainer portion. They may be created during molding or can be done by a secondary operation such as cutting, grinding or laser scoring performed after a manufacturing step of integrally molding the instrument panel and door. Current systems also include tear seams formed in back surfaces opposite the outer class-A surfaces of integral instrument panel/air bag door structures to improve the aesthetic appearance of the instrument panel by concealing the presence of the door.
To date, most tear seams formed in hard instrument panel retainers during molding are created via a reduced thickness of material. However, this method has proven unreliable where the structure of one side of the tear seam is limited to the nominal thickness of the panel. In such an instance the tearing action tends to leave the path of the intended seam which is unacceptable. Consequently, secondary operations are often used to increase the repeatability and robustness of the tear seam which has the negative impact of cutting cost.
At least one automotive instrument panel, as shown and described in U.S. Pat. No. 5,162,092, issued to Klobucar et al., discloses an instrument panel having a gas channel and a method for forming the channel in the panel. The gas channel is a tubular structure integrally formed in the panel by injecting gas into molten panel material in a mold. The gas channel in the Klobucar et al. instrument panel adds structural rigidity. However, Klobucar et al. does not disclose an air bag door or any other supplemental inflatable restraint component.
What is needed is a supplemental inflatable restraint system that includes an integrally formed air bag door having retaining structure that retains the door during air bag deployment and that can be formed with the air bag door instead of requiring a secondary operation. What is also needed is such a system that includes tear-guiding structure that guides tearing during air bag deployment and that can be formed with the air bag door instead of requiring a secondary operation.